Various sugar chain structures containing a sialic acid have been found in gangliosides and glycoproteins. For example, some sialic acid-containing polysaccharides have been found in capsular components of certain pathogenic bacteria. The capsular polysaccharide isolated from Neisseria meningitidis Serotype C is composed of a single polymer consisting of N-acetylneuraminic acids connected with .alpha.2 .fwdarw. 9 bond. .sup.13 C NMR spectroscopic study has revealed that the polymer (at 8- or 9-position) has partially O-acetylated structures (A. K. Bhattachariee, H. J. Jennings, C. P. Kenny, A. Martin, I.C.P. Smith, J. Biol. Chem., 250, 1926-1932, 1975). In addition, it has been reported that the capsular polysaccharide isolated from Escherichia coli Bos 12 is also a hetero-polymer having both .alpha.2 .fwdarw.9 and .alpha.2 .fwdarw. 8 bonding structures and that the capsular polysaccharide isolated from Escherichia coli K1 is a homo-polymer having .alpha.2 .fwdarw.8 bonding structures (W. Egan, T. Y. Lui, D. Dorow, J. S. Cohem, J. D. Robine, E. C. Gotschlich, J. B. Robins, Biochemistry, 16, 3687-3692, 1977). Some of polysaccharides produced by bacteria have recently been found to have pharmacological activities such as immuno-stimulating activity and antitumor activity (E. C. Gotschlich, B. A. Franser, O. N. Shimura, J. B. Robbins, T. Y. Lui, J.Biol, Chem., 256, 8915-8921, 1981). They are substances of interest from their pharmacological activities.
However, any process for chemical preparation of oligosialic acids as well as aforementioned sialic acid-containing polysaccharides has not been reported to date.
Accordingly, an object of the present invention is to provide oligosialyl-1,2-dialkyl-sn-glycerols which are derivatives of oligosialic acids and synthetic intermediates for their preparation. In addition, the present invention provides a process for preparing said oligosialyl-1,2-dialkyl-sn-glycerols.